Control system



R. C. SABINS CONTROL SYSTEM Aug. 29, 1961 2 Sheets-Sheet 1 Filed May 9,1958 INVENTOR. 20/49/70 C fab/715 ATTORNEYJ' R. C. SABINS CONTROL SYSTEMAug. 29, 1961 Filed May 9, 1958 2 Sheets-Sheet 2 JNVENTOR. Pol/and Cjab/n5 ATTORNE v5 2,998,371 CONTROL SYSTEM Rolland C. Sabins, 522Catalina Blvd, San Diego, Calif.,

assignor of forty-five percent to Bruce Dohrrnann, San

Francisco, Calif, and ten percent to A. K. Lindsay,

Walnut Creek, Calif.

Filed May 9, 1958, Ser. No. 734,322 11 Claims. (Cl. 204196) Thisinvention relates generally to a control system and method and moreparticularly to a control system and method for automatically providingcathodic protection for various types of structures, vessels and thelike which are normally submerged in water or some solution which actsas an electrolyte.

As is well known, the current requirement to provide satisfactoryprotection is dependent upon many factors, as for example, the speed ofmovement of the hull through the water, temperature, and ionic contentof the water through which the hull is moving, etc. Attempts to provideautomatic control to take care of these variations have heretofore notbeen completely satisfactory. This, in large part, has been due to thefact that apparatus of this type must function for long periods of timewithout maintenance because a ship carrying the system may not return toits home port for months and even years. Automatic control is alsocomplicated by the fact that the system must operate over a wide rangeof impressed currents. It must respond to very small control currentsand must provide magnification of a very high order. There is a need foran automatic control system which will be suitable for use on largevessels and which will require very little, if any, maintenance.

In general, it is an object of the present invention to provide animproved control system and method which will automatically control thecurrent impressed on the structure to be protected to maintain thestructure at a predetermined polarization.

Another object of the invention is to provide a system of the abovecharacter in which the reference cell is periodically rejuvenated to itsstandard reference level.

Another object of the invention is to provide a system of the abovecharacter in which the reference current is utilized for operating ameter movement.

Another object of the invention is to provide a system of the abovecharacter in which the meter movement controls the flow of light to alight sensitive cell.

Another object of the invention is to provide a system of the abovecharacter in which the output of the light sensitive cell serves tocontrol the means for impressing the current on the structure to beprotected.

Another object of the invention is to provide a system of the abovecharacter in which the reference cells are provided in banks.

Another object of the invention is to provide a system of the abovecharacter wherein a reference cell of the bank is utilized forcontrolling the monitoring circuit, another is utilized for driving avisual indicating voltmeter and another is utilized for driving arecording type instrument.

Another object of the invention is to provide a system of the abovecharacter in which the reference cells are periodically rejuvenated insequence.

Another object of the invention is to provide a system of the abovecharacter in which one reference cell of a plurality of reference cellsis always connected to the monitoring circuit.

Another object of the invention is to provide a system of the abovecharacter in which the means for impressing current on the structureincludes saturable core reactors.

Another object of the invention is to provide a system 2,993,371Patented Aug. 29, 1961 of the above character in which the saturablecore reactors can be paralleled to increase the impressed current flow.

Another object of the invention is to provide a system of the abovecharacter which has practically no moving parts and which requires. verylittle, if any maintenance.

Another object of the invention is to provide a system and method of theabove character which utilizes a high order of magnification.

Another object of the invention is to provide a system and method of theabove character with wide ranges of impressed current flow.

Another object of the invention is to provide a system of the abovecharacter in which the response is almost instantaneous and closelyfollows the demand.

Additional objects of the invention will appear from the followingdescription in which the preferred embodiments have been set forth indetail in conjunction with the accompanying drawing.

Referring to the drawing:

FIGURE 1 is a circuit diagram incorporating the present invention withcertain parts illustrated schematically;

FIGURE 2 is a portion of a circuit diagram for a system with a higherpower output than that shown in FIGURE 1;

In general, the present invention comprises a control system and methodfor automatically providing cathodic portection for various types ofstructures such as the hulls of vessels and barges and like normallyimmersed or submerged in fresh or salt water or other electrolyte, Acurrent is impressed on the structure to cause the structure to serve asa cathode. A monitoring circuit is provided in which a reference currentis generated and this reference current is utilized for controlling theamount of current impressed on the structure to maintain the structureat a relatively constant predetermined polarization to prevent corrosionof the structure.

As shown in FIGURE 1 of the drawing, my control system comprisesgenerally an impressed current power supply 11, monitoring means whichincludes a reference current supply and control 12 and means 13 forrejuvenating the reference current supply. The impressed current supply11 is connected between an anode assembly 114 and a structure 16 to beprotected which is represented as ground. The anode assembly 14 and thestructure 16 are shown submerged or immersed in an electrolyte 17 which,for example, can be sea water. The structure to be protected can be thehull of a ship as shown and the anode assembly 14 can be of any suitabletype such as that disclosed in my copending application entitledElectrolytic System, Serial No. 715,440, filed February 14, 1958.

The monitoring means 12 includes one or more reference cells 21 whichare utilized for generating a reference current. As shown, the referencecells are also submerged in the electrolyte 17 and are generally mountedrelatively close to the structure 16 to be protected. The referencecells can be of any suitable type such as the silver-silver chloridereference half cells well known to those skilled in the art. Suchreference half cells have a potential in the electrolyte 17 whichdiffers from the potential of the structure 16 when it is submerged inthe electrolyte so that there is a current flow between the referencecells and the structure 16 to be protected. When reference cells of thesilver-silver chloride type are utilized, the reference cells have arelatively uniform potential which is approximately 630 millivolts lowerthan that of a steel hull of a ship, if for example, that is thestructure to be cathodically protected.

When the reference cell is connected by a conductor to the hull of theship, current will flow through the electrolyte 17, from the hull of theship to the reference half cell. By current flow, I am referring to theflow of electrons from negative to positive or rather a lower negativethan the conventional designation of current flow from positive tonegative.

As is well known to those skilled in the art, the silversilver chloridereference half cells have a relatively constant potential when immersedin an electrolyte and for that reason the current flow from the hull ofthe ship to the reference half cells will be dependent upon thepolarization level on the hull of the ship or the structure beingcathodically protected. When the polarization level of the ship isrising, the current flow between the hull of the ship and the referencehalf cells will increase, and conversely when the polarization level ofthe hull of the ship begins to fall, the current flow between the hullof the ship and the reference half cells will decrease.

The reference cells 21, as shown in the drawing, are connected to atiming device 23 for a purpose hereinafter described. As shown, and ashereinafter described, one of the reference half cells is normallyconnected by a conductor 24 to the positive terminal of a meter 26, thenegative terminal of the meter being connected to ground as shown. Aspointed out previously, all points designated as ground, are actuallyconnected to the structure 16 to be protected as, for example, the shipsground when the hull of a ship is being protected. The meter 26 is of asuitable type such as a sensitive D.C. millivoltmeter. The meter 26 hasa relatively high resistance in the order of 100,000 ohms per volt ormore which prevents any appreciable reference current flow. This servesto prevent rapid polarization of the reference half cells which wouldotherwise occur if there were appreciable reference current flow. Thesilver-silver chloride reference half cells therefore serve as reliablereferences and only require depolarization as hereinafter described atperiodic intervals.

The reference half cells 21 as shown in the drawing are designated aspositive. This has been done because even though the reference cells areactually negative, they are less negative than a steel hull and thus arepositive with respect to the steel hull or structure 16. The referencecells have been designated in this manner to facilitate understanding ofthe direction of current flow.

The meter 26, as shown schematically, includes a needle-like pointer orhand 27 which has a spade-like tip 28. The dial 29 of the meter isprovided with a hole 31 which is adapted to be covered by the spade-liketip 28 of the pointer when the meter is indicating a midpoint positionas shown in the drawing. A stop 32 is provided on the dial face toprevent the pointer from advancing beyond the midpoint of the dial.Since the meter 26 is connected in series between the reference halfcells and the structure to be protected, it is apparent that the meter26 will register the reference current flow between the structure 16 andthe reference half cell 21 to which it is connected.

A suitable light source such as a lamp 34 is positioned on one side ofthe dial face 29, for example, as shown it is positioned in front of thedial face. The lamp 34 is connected to a suitable source of power suchas 110 volts, 60 cycle single phase A.C. as designated by the terminalsL1 and L2. As shown, the lamp is connected across the terminals L1 andL2 through a variable series resistor 36. The lamp 34 is preferably of atype with a very long life such as years. The resistor 36 is provided tovary the intensity of the light from the lamp.

Suitable light sensitive means 37 is mounted on the other side of thedial face opposite the opening or hole 31. For example, apolycrystalline photoconductive cell can be utilized. Particularly, acadmium-selenide photo cell has been found to be especiallysatisfactory. The light sensitive means 37 is preferably mountedrelatively close to the hole 31 and, for example, may be mounted withinthe meter housing itself if desired.

As shown, the output of the light sensitive means 37 is connected to apower reactor 39 in series with an ammeter 41. The ammeter 41 is of anysuitable type such as a very sensitive D.C. microammeter. The powerreactor 39 is of the saturable core type with duplex windings wound on apair of toroidal cores. As shown, the reactor 39 comprises a pair oftoroidal cores 42, a DC. saturating winding 43, a pair of A.C. or outputwindings 44, a DC bias winding 46, and a DC. shorted winding 47.

The shorted winding 47 is provided to prevent breakdown of theinsulation within the power reactor 39 and to prevent damage to othercomponents in the circuit hereinafter described. In the event the A.C.power to the A.C. ouput windings 44 should be suddenly interrupted, thesudden collapse of the lines of force in these coils would normallyinduce several thousand volts into the D.C. windings of the reactor and,therefore, would have a tendency to cause the damage hereinbeforedescribed. However, the shorted coil which has a very low impedanceprevents such an occurrence by shorting out the induced current andthereby preventing the build-up of dangerous voltages within the otherwindings of the reactor.

The bias winding 46 is wound in the opposite direction to that of themain saturating winding 43 and its purpose is to bias the output of theA.C. windings 44 to cut off when saturating current is not applied tothe saturating windings. The bias winding 46 is supplied from the A.C.power supply designated by the lines L1 and L2 through a transformer 49which has its output connected to a pair of suitable rectifiers 51. Therectifiers 51 are connected to one side of the bias winding 46 and theother side of the bias winding is connected to the centertap 52 of thesecondary winding of the transformer 49 through a serially connectedshunt resistance 53 and a variable resistance 54. An amrneter 56 of asuitable type, such as a DC microammeter, is connected across the shuntresistance 53. The variable resistance 54 is provided to adjust the flowof current in the bias winding 46. As is well known to those skilled inthe art, the current How in the bias winding must be carefully adjustedso that the load from the output windings 44 is zero when the input tothe DC. saturating winding is at zero.

As shown, one side of the output of the light sensitive means 37 isconnected to one side of the DC. saturating winding 43 and the otherside of the DC. saturating winding is connected to the center tap 52 ofthe secondary of the transformer 49. The other side of the output of thelight sensitive means is connected to the side of the bias winding 46which is connected to the rectifiers 51.

The output of the A.C. windings 44 of the reactor 39 is connected acrossa full wave bridge 59 comprising four rectifiers 61. The center tap 62between the A.C. windings 44 is connected to the A.C. line L2 by aconductor 63. The other side of the rectifier bridge is connected to theA.C. line L1 by conductor 65.

The output from the full wave bridge 59 is supplied to the power reactor64. The power reactor 64 comprises a pair of closed C-type cores 66, apair of DC. saturating windings 67, four A.C. windings 68, a variableresistance 69 and a fixed resistance 71. The power reactor 64 is woundin such a manner that magnetic opposition is provided under alloperating conditions and for that reason a bias winding of the typeprovided in the power reactor 39 is not required. A bias is also notused because the winding arrangement utilized in the power reactor 64 isnot of a type which lends itself to the use of a bias winding. Thewindings and the core material have been chosen so that the output ofthe A.C. windings 68 is zero or substantially zero when there is noinput to the DO. saturating windings 67.

The output of the full wave bridge 59 is connected across the seriallyconnected D.C. saturating windings 67 of the power reactor 64 byconductors 73 and 74.

An ammeter 76 is connected in a series with the conductor 74 and can beof any suitable type such as a DC. milliammeter.

It will be noted that the resistances 69 and 71 are serially connectedacross the conductors 73 and 74 and in parallel with the DC. saturatingwindings 67. These resistances 69 and 71 have been inserted in the powerreactor because it was found that the normal sinusoidal full wave D.C.output from the full wave bridge 59 would not cause proper operation ofthe DC. saturating windings 67. In fact, it was found that thesaturating windings 67 were actually acting as a choke coil because ofthe back induced by the rapidly fluctuating sinusoidal full wave D.C. Byutilizing the resistances 63 and 71 in parallel with the DC. windings,the resistances serve to bypass or cut oif the peaks of the sinusoidaloutput from the full wave bridge. Thus, the DC. peaks pass through theresistances and not through the DC. saturating windings. The rapidfluctuations of the DC. in the windings 67 and the generation of backare eliminated. it is apparent that capacitors could be utilized for thesame purpose of smoothing out the DC. However, resistors have beenchosen because they have much longer life. A pi type filter can also beused for such a purpose and can consist of iron core inductance and apair of dry plate type capacitors.

The output of the power reactor 64 is fed into an A.C.-DC. rectifiersection 78. As shown, the four A.C. windings of the power reactor areconnected in series opposition and have one end connected to the A.C. orconductor 65 and the other end connected to the primary winding of anisolation transformer 79. The other side of the primary is connected tothe line L2 of the A.C.

supply. The secondary of the isolation transformer is connected across afull wave bridge 81 comprising four rectifiers 82. The positive terminalof the output of the full wave bridge 81 is connected to the anodeassembly 14 by a conductor 33, and the negative or ground terminal ofthe bridge is connected to the structure 16 by conductor 84. A DC.ammeter 86 is connected in series with the conductor 63. A DC. voltmeter87 is connected across the output of the full wave bridge 81.

Operation of that portion of the system hereinbefore described may nowbe briefly described as follows: Let it be assumed that themillivoltmeter 26 has been adjusted by adjustment of its externalresistance (not shown) so that at the desired polarization on thestructure 16, the needlelike pointer 27 of the meter is at its midpointposition and the spade-like tip of the needle is covering the hole 31 inthe dial face. The spade-like tip 28 in this position prevents theentrance of light rays through the hole 31 and therefore preventsactivation of the light sensitive means 37. The pointer 27 in thisposition is against the needle stop 32 so that at increased polarizationlevels of the structure 16 above the desired polarization, no light canpass through the opening 31.

Now let it be assumed that the structure 16 has dropped below thedesired level of polarization which is required for cathodic protection.When this occurs, the potential difference between the reference cells21 and the structure 16 decreases, which in turn causes a decrease inthe reference current flow in direct proportion to the decrease in thepotential difference. The difference in the decrease in the current flowis registered by the meter 26 and the pointer 27 begins to move towardsa decreased current position. As soon as the pointer 27 has moved fromits midpoint position, the spade-like tip 28 exposes the hole 31 andpermits light from the lamp 34 to enter the hole and activate the lightsensitive means or cell 37.

Activation of the light sensitive cell 37 reduces its re-- sistance sothat it permits substantial current flow in the D.C. saturating windings43 of the power reactor 39. Current flow is from the center tap 52through the DC. saturating winding 43, through the resistance of thelight sensitive cell 37, through the microammeter 41 and to the positiveside of the rectifiers 51.

The flow of current through the DC. winding 43 saturates the toroidalcores 42 to permit flow of A.C. current in the output windings 44, byeliminating the impedance in the output windings 44. The A.C. outputfrom the windings 44 is rectified by the full wave bridge 5? and the DC.from the bridge is supplied to the DC. saturating windings 67 of thepower reactor 64. The flow of DC. current in the saturating windings 67saturates the cores 66 which reduces the impedance in the A.C. windings68 to permit A.C. to pass through these power windings and to energizethe isolation transformer 79. The A.C. output from the isolationtransformer is rectified by the main full wave bridge 81 to deliver apositive DC. current to the anode array 14-. The negative terminal ofthe bridge 81 is connected to the structure 16 to be protected.

The increased potential difference between the structure 16-and theanode assembly 14- will cause increased current to flow from thestructure 16 to the anode array by electrochemical exchange through theelectrolyte 17. As the current flow increases, the polarization level ofthe structure 16 will increase. As the polarization of the structure 16increases, the potential difference between the reference cells 21 andthe structure 16 also increases. As this potential difference increases,the reference current flowing from the structure 16 to the referencehalf cells will also increase causing the millivoltmeter 26 to registeran increase. This will continue until the spade-like tip 28 of thepointer 27 again covers the hole 31 in the dial 29.

From the foregoing description, it is apparent that as soon as thepolarization level of the structure 16 drops below the predetermineddesired level, the spade-like tip 23 will uncover the opening 31 tocause a sequence of operation which will increase the current flowbetween the structure 16 and the anode 14 until the increase issufficient to raise the polarization level of the structure 16 to thedesired level. Thus, the polarization level of the structure 16 ismaintained relatively constant. If there are no changes in thepolarization level, the spade-like tip 28 will cover the opening 31 anda relatively constant flow of current will occur between the structure16 and the anode 14., When there are changes in the polarization level,the response of the system is almost instantaneous'and the polarizationis rapidly built up to the desired level.

'As hereinbefore described, my system includes means 12 for continuouslymonitoring the polarization on the structure being cathodicallyprotected. This monitoring means which has also been referred to as thereference and current supply has been previously described as includingreference cells 21. It has been found that these reference half cells donot maintain an absolutely constant level of polarization, but that whenthey are subjected to various environments and are employed in acathodeanode couple they gradually become negatively polarized. Whenthis occurs, the reference cells fail to serve the function of aconstant reference.

It has however been found that by periodically rejuvenating ordepolarizing the reference half cell by reversing the cathode-anodecouple arrangement at periodic intervals, the reference half cells aremaintained at a relatively constant polarization level so that they caneffectively monitor the polarization level of the structure to beprotected. To that end, the means 13 has been provided for periodicallyrejuvenating the reference half cells and consists of a timing device23, a transformer 91 and a rectifier assembly 32.

The timing device, as shown, consists of four collector rings 93 and acommutator 94. The collector ring 93 and the commutator 94 are mountedon the same shaft and are all driven at the same speed by the motor 96.The collector rings and commutator can be driven at any suitable speedas, for example, six revolutions per hour.

7 The motor 96 is connected to a suitable source of power such as thelines L1 and L2 which as hereinbefore described are connected to an A.C.supply.

As shown in the drawing, each of the reference half cells 21 isconnected to one of the collector rings 93 by a brush 97. The brush 97and the collector rings 93 are preferably formed of materials which havea relatively long life. For example, the collector rings can be made ofsilver and the brushes 97 can be of the silver-carbon type. Thecollector rings 93 are connected to a commutator 94. As shown, thecommutator 94 is divided into four segments 94a, 94b, 94c and 94d, eachof which is connected to one of the collector rings 93.

Three brushes 98, 99 and 101 are provided which engage the commutator94. Brush 98 is connected to the conductor 24 which is connected to themeter 26. Brush 99 is connected to the positive side of a rectifierassembly 92 and brush 101 is connected to a suitable recordinginstrument 103 by a conductor 104.

The rectifier assembly 92 consists of a pair of rectifiers 106 which areconnected to the secondary of the transformer 91. A variable resistance107 is connected between a tap on the secondary of the transformer 91and ground. The primary of the transformer 91 is connected to a suitablesource of AC. power such as the lines L1 and L2 as shown.

Operation of the rejuvenating means 13 may now be briefly described asfollows: Let it be assumed that to cathodically protect the structure 16that it is necessary to maintain the structure 16 at a predeterminedpolarization level with respect to the reference cells 21, as forexample, 1000 millivolts. If such is the case, the resistance 107 of therectifier assembly 92 is adjusted so that the rectifier assembly 92 willdeliver 1000 millivolts on the conductor 13 through the timing device23.

With the timing device 23, one of the reference cells 21 is alwaysconnected to the millivoltmeter 26 by the brush 98. As explainedpreviously, when the reference cells 21 are connected to the structurebeing protected through the millivoltmeter 26, there is an electron flowfrom the structure being protected to the reference cells. After a cellhas been utilized as a reference cell by being connected to themillivoltmeter 26, it is rejuvenated when it comes in contact with thebrush 99. As hereinbefore explained, the brush 99 is connected to thepositive side of the rectifier assembly 92. When the reference cell isconnected to the positive voltage, the electron flow between thereference cell and the structure 16 being protected is reversed torestore the reference half cell to its original anodic state withrespect to the structure being protected. By thus periodically applyinga positive voltage to the reference half cells, the reference half cellsare maintained in an anodic state and do not have an opportunity tobecome partially cathodic with respect to the structure being protected,as for example, the steel hull of a ship.

It should be pointed out that a positive voltage is applied to thereference half cell which is equal to the polarization level of thestructure to be protected. This is done to prevent an over-voltage frombeing applied to the millivoltmeter 26. As pointed out previously, themillivoltmeter 26 has a mechanical stop 32 which prevents the indicatingneedle 27 from passing beyond or past the hole 31.

With the timing device 23 as shown in the drawing, each of the referencecells will be under the rejuvenating influence of the positive voltagefrom the rectifier assembly 92 for approximately 25% of the totalelapsed time. After the rejuvenation is completed, the circuit to thereference half cell is broken and it is not used for approximately 25%of the elapsed time since only three brushes are provided in the timingdevice 23. During the time in which the reference cell is idle, thereference cell has an opportunity to stabilize itself. After this periodof time, the reference cell is again engaged by the brush 98 and isconnected to the millivoltmeter 26.

In large installations of my system, it may be desirable to providemeans for continuously recording the polarization level of the structurebeing protected. To this end, I have provided a recorder 103 which isconnected to the brush 101. The brush 101 is always in engagement withone of the segments of the commutator 94 and, therefore, provides acontinuous signal to the recorder 103. The recorder 103 can be of anysuitable type such as those which utilize a moving pen to give a writtenindication on a continuously moving strip chart.

With the system hereinbefore described, one of the reference half cells21 is always connected to the millivoltmeter 26 to provide continuousmonitoring for the system. However, if it is desired to simplify thesystem to reduce the cost, or for other reasons, it is possible to useonly one reference cell 21 for operation of the millivoltmeter 26. Withsuch a system, the reference half cell could be periodicallydisconnected from the meter for a sufficient period of time andconnected to the positive voltage of the rectifier assembly 92 by asimple timing device to rejuvenate the half cell. After rejuvenation iscompleted, the reference cell could again be connected to the meter 26.During the short period of time the reference half cell is beingrejuvenated, the polarization of the ship would be allowed to decrease.This is not objectionable because of the short period of time requiredfor rejuvenation of the half cell, as for example, one minute out ofevery hour.

By way of example, one embodiment of my system utilized componentshaving the following designations, values and characteristics.

Diodes:

51 1N1084. 61 1N1092. 82 1N1167and1N1181. 106 1N1084.

Photocell 37 Clairex type CL-3. Transformers 49 110 volts to 25 volts.91 w 110 volts to 25 volts. 79 1:1 ratio, 1000 watt capacity. Saturablecore reactors:

39 Output of 500 milliamperes. -64 1000 watt capacity. Meters:

26 0-300 maximum millivolts adjustable. 41 0-500 microamperes. 56 0-1milliampere, shunted to obtain desired milliampere range. 76 0-500microamperes. 87 0100 volts. 86 0-100 amperes. Resistances:

36 Wire wound, ohms. 54 Wire wound, 1000 ohms. 69 Wire wound, 500 ohms.71 Wire wound, 25 ohms. 107 Wire wound, 1 megohm.

It has been found that a system having the above components has amplecapacity to provide complete cathodic protection for a ship feet inlength with a steel hull, and having approximately 5000-6000 square feetof wetted surface. With the 1000 watts available from such a system, theampere voltage ratio is automatically determined by the ratio of thesurface of the anode assembly 14 utilized and the wetted surface of thestructure to be protected, and the resistivity of the water orelectrolyte. Thus, if a 1:1 isolation transformer 79 is utilized and theisolation transformer is driven from a 115 volt, 60 cycle, single phaseA.C. supply and the power reactor 64 is being driven at its full 1000watts output, the DC. voltage on the output read by the meter 87 wouldbe approximately 20 volts and the amperes read by the meter 86 would beapproximately 50 amperes, as

suming that the proper amount of anode surface was utilized to obtainthe proper anode-cathode ratio, and also assuming that the structure isin water having a relatively high resistance. If the structure were avessel operating in the equatorial zones in warm water with lowresistivity, the DO. voltage might be as low as 10 volts with 100amperes D.C.

With a system of the above type having an output of 1000 watts, anamplification of two hundred million to one is achieved by only twostages of amplification as represented by the reactors 39 and 64. Thereference cells have an output of approximately 10 microwatts. Onlyone-half of the output, microwatts, is utilized for driving the meter26. These 5 microwatts are amplified into the 1000 watts in the outputto give the two hundred million to one power amplification.

Since the current flow from the structure being protected such as thehull of a ship to the anodes l4 determines the polarization level of thestructure being protected, it is important that a wide range of currentflow be obtainable from any satisfactory system. Generally, it isdesirable to obtain a 50 to 1 variation in current flow. With my system,it has been found possible to obtain a 100 to 1 variation in the currentflow.

I have found by utilizing the light sensitive cell 37, precise controlcan be obtained on the polarization level of the structure beingprotected. If the polarization level of the structure being protectedshould drop only a very slight amount below the desired level, thesystem immediately determines this condition and responds practicallyinstantaneously to increase the current flow from the impressed currentmeans. The system is instantly cognizant of any changing conditionswhich may require increased or decreased current flow, as for example,in the case of a vessel which is passing through water which hasdifferent resistance characteristics than that previously passedthrough.

In the event additional power output is required in a system forcathodic protection, my system can be easily modified to make more poweravailable. For example, as shown in FIGURE 2 of the drawing, the outputof the power reactor 64 can be utilized for supplying the DC. saturatingcurrent for additional reactors. For example, as shown, the output ofthe reactor 64 can be passed through a full wave bridge 111 consistingof four rectifiers 112 connected in a conventional manner. The output ofthe bridge 111 is connected to the DC. saturating coils 67 of a pair ofpower reactors 64 identical to the power reactor hereinbefore described.The power reactors are connected in parallel as shown and have theiroutputs connected to an A.C.-D.C. rectifier section 1% similar tosection 78, but of a larger size.

The remainder of the system would be identical to that shown in FIGURE 1and for that reason it has not been shown in FIGURE 2.

Thus, it is apparent that any range of power requirements can beobtained with my system with the use of many standardized parts. Forexample, the system as shown in FIGURE 2, with the power reactor 64connected in parallel, would have a D0. power output of 42,500 wattswhich would be controlled by the 5 microwatts output from the referencecells 21. Thus, with such a system, an amplification of eighty-fivebillion to one can be obtained with three stages of amplificationwithout any sacrifice in the quality of control.

It is apparent from the foregoing that I have provided a completelyautomatic control system and method for maintaining a desiredpolarization level on a structure to be cathodically protected. Thereare no moving parts in the system except for the slowly moving parts inthe timing device 23 and in the meter movements which have an extremelylong life. Thus, in contrast to other systems, my system has nomechanical relays, contact points, servo mechanisms, variacs or othermoving parts which would require extensive and continued maintenance. Byutilizing saturable core reactors, magnifications of a high order areobtained by devices which have a relatively long life and require nomaintenance. By utilization of the light sensitive means, a particularlyprecise control is obtained which has an almost instantaneous responseand which closely follows the demand on the system. Such performancecoupled with the lack of maintenance is particularly important insystems of this type which are often installed in large ships which maynot return to their home ports for long periods of time. If this werenot the case, a breakdown of the system while the ship was out of portcould permit severe damage to occur to the hull of the ship before thesystem could again be placed in operation.

It is also apparent that in addition to being useful for the cathodicprotection of the hulls of ships, barges and other floating vessels mysystem can be used for cathodically protecting other structures such asunderwater foundations, pipelines, storage reservoirs, and the like.

While the form of embodiment herein shown and described constitutes apreferred form, it is to be understood that other forms may be adoptedfalling within the scope of the claims that follow.

I claim:

1. In a control system for cathodically protecting a structure immersedin an electrolyte, an anode immersed in the electrolyte, saturable corereactor amplification means connected to said anode and said structureto impress a current fiow between the anode and the structure to causethe structure to serve as a cathode, and reference means immersed in theelectrolyte, the reference means having a relatively constant potentialin the electrolyte which differs from the potential of said structure tobe cathodically protected so that there is a reference current flowbetween the structure and the reference means, a meter having a pointerand an opening adapted to be closed by the pointer, said meter beingresponsive to the reference current flow between the structure and thereference means, a light source adapted to shine through the opening ofsaid meter and being in a position on one side of said pointer, lightsensitive means positioned on the other side of said pointer and beingadapted to receive light passing through said opening, said meter beingcalibrated and said opening in the meter being positioned so that at apredetermined flow of reference cunrent said pointer overlies saidopening and prevents the passage of light through said opening, andmeans connected to said light sensitive means for regulating said meansfor impressing current flow between the anode and the structure.

2. In a control system for cathodically protecting a structure immersedin an electrolyte, an anode immersed in the electrolyte, means connectedto said anode and said structure to impress a current flow between theanode and the structure to cause the structure to serve as a cathode,said means including a pair of saturable core reactors, reference meansimmersed in the electrolyte, the reference means having a relativelyconstant potential in the electrolyte which differs from the potentialof said structure to be cathodically protected so that there i areference current flow between the structure and the reference means,and means responsive to the reference current flow between the referencemeans and said structure to regulate said means for impressing currentflow between the anode and the structure to maintain a relativelyconstant predetermined polarization potential on said structure.

3. In a control system for cathodically protecting a structure immersedin an electrolyte, an anode immersed in the electrolyte, means connectedto said anode and said structure including a saturable core reactoramplification means to impress a current flow between the anode and thestructure to thereby cause the structure to serve as a cathode,reference means disposed in the electrolyte, the reference means havinga relatively constant potential in the electrolyte which differs fromthe potential of said structure to be cathodically protected so thatthere is areference current flow between the structure and the referencemeans, and means responsive to the reference current flow between thereference means and said structure and connected to said means forimpressing current flow between the anode and the structure to regulatethe means for impressing current flow to maintain a relatively constantpredetermined polarization potential on said structure, said last namedmeans including light sensitive means having a relatively highresistance when no light is being received and a relatively lowresistance when light is being received.

4. In a control system for cathodically protecting a structure immersedin an electrolyte, an anode immersed in the electrolyte, means connectedto said anode and said structure including saturable core reactoramplification means to impress a current flow between the anode and thestructure to thereby cause the structure to serve as a cathode,reference means disposed in the electrolyte, the reference means havinga relatively constant potential in the electrolyte which differs fromthe potential of said structure to be cathodically protected so thatthere is a reference current flow between the structure and thereference means, and means responsive to the reference current flowbetween the reference means and said structure and connected to saidmeans for impressing current flow between the anode and the structure toregulate the means for impressing current flow to maintain a relativelyconstant predetermined polarization potential on said structure, saidreference means comprising a plurality of reference cells together withmeans for continuously connecting one of said cells to said meansresponsive to reference current flow, and means for periodicallydepolarizing each of said cells when it is not connected to said meansresponsive to reference current flow.

5. A control system as in claim 2 wherein one of said saturable reactorsutilizes a pair of toroidal shaped cores and the other of said reactorsutilizes a pair of C-type cores.

6. A control system as in claim 5 wherein the other of said reactors isprovided with a DO saturating winding and filtering means in parallelwith the saturating winding.

7. In a control system for cathodically protecting a structure immersedin an electrolyte, an anode immersed in the electrolyte, means connectedto said anode and said structure to impress a current fiow between theanode and the structure to cause the structure to serve as a cathode, aplurality of reference cells, the reference cells having a relativelyconstant potential in the electrolyte which differs from the potentialof said strcture to be cathodically protected so that there is areference current flow between the structure and each of the referencecells when a circuit is established between each of the reference cellsand the structure, a light source, light sensitive means positionedadjacent said light source, means responsive to the reference currentflow for interrupting the passage of the light beam from the lightsource to the light sensitive means, means responsive to said lightsensitive means for regulating said means for impressing current flowbetween the anode and the structure to maintain a relatively constantpredetermined polarization potential on said structure, and a timingdevice for periodically and sequentially connecting said reference cellsof said means responsive to reference current flow.

8. A control system as in claim 7 wherein said timing device includes aplurality of slip rings, each of said reference cells being connected toone of said slip rings, a commutator formed of a. plurality of segments,each of said collector rings being connected to one of said segments,and brush means for engaging said segments one at a time to supplyreference current to said means responsive to reference current flow,and means for driving said collector rings and said commutator insynchronization.

9. A control system as in claim 8 together with additional brush meansspaced from said first named brush means and adapted to engage thesegments of said commutator, and a source of positive DC. voltageconnected to said additional brush means to depolarize the referencecells as they come into electrical contact with said additional brushmeans.

10. In a control system for cathodically protecting a structure immersedin an electrolyte, an anode immersed in the electrolyte, means connectedto said anode and said structure to impress a current flow between theanode and the structure to cause the structure to serve as a cathode,reference means immersed in the electrolyte and connected to thestructure, the reference means having a relatively constant potential inthe electrolyte which differs from the potential of said structure to becathodically protected so that there is a reference current flow betweenthe structure and the reference means through the electrolyte and meansresponsive to the reference current flow between the reference means andsaid structure to regulate said means for impressing current flowbetween the anode and the structure to maintain a relatively constantpredetermined polarization potential on the structure, the referencemeans comprising a plurality of reference cells together with means forcontinuously connecting one of said cells to said structure and meansfor periodically depolarizing each of said cells when it is notconnected to said means responsive to reference current flow.

11. In a control system for cathodically protecting a structure immersedin an electrolyte, an anode immersed in the electrolyte, means connectedto said anode and said structure to impress a current flow between theanode and the structure to cause the structure to serve as a cathode,reference means continuously immersed in the electrolyte and constantlyconnected to the structure, the reference means having a relativelyconstant potential in the electrolyte which differs from the potentialof said structure to be cathodically protected so that there is areference current flow between the structure and the reference meansthrough the electrolyte, and means responsive to the reference currentflow between the reference means and said structure to regulate saidmeans for impressing current flow between the anode and the structure tomaintain a relatively constant predetermined polarization potential onsaid structure, the reference means comprising a plurality of referencecells, means for sequentially connecting and disconnecting said cells tosaid structure and means for sequentially depolarizing said cells whennot connected to said structure.

References Cited in the file of this patent UNITED STATES PATENTS2,221,997 Polin NOV. 19, 1940 2,759,887 Miles Aug. 21, 1956 2,765,986Pompetti et al. Oct. 9, 1956 2,918,420 Sabins Dec. 22, 1959 FOREIGNPATENTS 669,675 Great Britain Apr. 9, 1952 OTHER REFERENCES Anal. Chem,vol. 23, pages 941-944, July 1951, De Ford.

Corrosion, vol. 13, May 1957, pp. 8-74, art. by Werner.

1. IN A CONTROL SYSTEM FOR CATHODICALLY PROTECTING A STRUCTURE IMMERSEDIN AN ELECTROLYTE, AN ANODE IMMERSED IN THE ELECTROLYTE, SATURABLE COREREACTOR AMPLIFICATION MEANS CONNECTED TO SAID ANODE AND SAID STRUCTURETO IMPRESS A CURRENT FLOW BETWEEN THE ANODE AND THE STRUCTURE TO CAUSETHE STRUCTURE TO SERVE AS A CATHODE, AND REFERENCE MEANS IMMERSED IN THEELECTROLYTE, THE REFERENCE MEANS HAVING A RELATIVELY CONSTANT POTENTIALIN THE ELECTROLYTE WHICH DIFFERS FROM THE POTENTIAL OF SAID STRUCTURE TOBE CATHODICALLY PROTECTED SO THAT THERE IS A REFERENCE CURRENT FLOWBETWEEN THE STRUCTURE AND THE REFERENCE MEANS, A METER HAVING A POINTERAND AN OPENING ADAPTED TO BE CLOSED BY THE POINTER, SAID METER BEINGRESPONSIVE TO THE REFERENCE CURRENT FLOW BETWEEN THE STRUCTURE AND THEREFERENCE MEANS, A LIGHT SOURCE ADAPTED TO SHINE THROUGH THE OPENING OFSAID METER AND BEING IN A POSITION ON ONE SIDE OF SAID POINTER, LIGHTSENSITIVE MEANS POSITIONED ON THE OTHER SIDE OF SAID POINTER AND BEINGADAPTED TO RECEIVE LIGHT PASSING THROUGH SAID OPENING, SAID METER BEINGCALIBRATED AND SAID OPENING IN THE METER BEING POSITIONED SO THAT AT APREDETERMINED FLOW OF REFERENCE CURRENT SAID POINTER OVERLIES SAIDOPENING AND PREVENTS THE PASSAGE OF LIGHT THROUGH SAID OPENING, ANDMEANS CONNECTED TO SAID LIGHT SENSITIVE MEANS FOR REGULATING SAID MEANSFOR IMPRESSING CURRENT FLOW BETWEEN THE ANODE AND THE STRUCTURE.